1. Field of the Invention
The present invention relates to a driving circuit which drives data lines in a display device for multigradation display of pixels.
2. Description of the Related Art
In active matrix liquid crystal display devices, which are the mainstream of liquid crystal display devices, pixels are selectively driven in units of pixels (dot sequential driving) or in units of rows (line sequential driving).
In an active matrix liquid crystal display device, pixels containing liquid crystal cells are arranged in the form of a matrix. Each pixel includes a thin film transistor (TFT), and a hold (retentive) capacitor which is connected in parallel to the liquid crystal cell. The hold capacitor is provided between the drain of the TFT and a predetermined common potential, and the source of the TFT is connected to a corresponding data line.
In the active matrix liquid crystal display devices disclosed in Japanese Patent Applications Laid-Open (JP-A) Nos. 2000-165244 and 2005-010276, the scan line is successively selected by a gate driver, and the TFTs of all of the pixels connected to the selected scan line (row) are turned on. While the TFTs of the selected row are on, gradation potentials corresponding to display data are supplied from a source driver via the data line to one ends of the hold capacitors of the pixels. The hold capacitors hold (retain), during the time period of a frame, the charges accumulated via the data line.
In recent years, as the size of liquid crystal panels has increased (i.e., as the number of data lines has increased), the circuit scale of the driving circuit which serves as the source driver which drives the TFTs has increased. Because the number of lines within the driving circuit thereby increases, the resistance (wiring resistance) parasitic on the lines increases, and the charging time period of the gradation voltage with respect to the hold capacity within the pixel becomes long. Accordingly, due to the size of liquid crystal panels increasing in recent years, the writing period to the pixels within the panels has not been able to be sufficiently ensured.
On the other hand, increasing the size of the chip for forming the driving circuit in order to reduce the wiring resistance is not preferable from the standpoint of costs.
For the above reasons, in the driving circuit of a display device, it has been desired to shorten the writing period to the pixels while avoiding an increase in the chip size.